Electrical characterization of ALD HfO2 high-k dielectrics on ( 2¯01) β-Ga2O3

The electrical quality of HfO2 dielectrics grown by thermal atomic layer deposition at 175 °C on n-type ( 2¯01) β-Ga2O3 has been studied through capacitance- and current-voltage measurements on metal-oxide-semiconductor capacitors. These capacitors exhibited excellent electrical characteristics, including dual-sweep capacitance-voltage curves with low hysteresis and stretch-out and a frequency-stable dielectric constant of k∼14 when measured between 10 kHz and 1 MHz. The C-V curves exhibited a uniform and repeatable +1.05 V shift relative to the ideal case when swept from 3.5 to −5 V, yielding positively measured flatband (+2.15 V) and threshold (+1.05 V) voltages that may be useful for normally off n-channel Ga2O3 devices. Using the Terman method, an average interface trap density of 1.3 × 1011 cm−2·eV−1 was obtained between 0.2 and 0.6 eV below the conduction band edge. The forward bias current-voltage characteristic was successfully fitted to the Fowler-Nordheim tunneling model at a field strength of 5...